Switchgears for medium and/or high voltage, e.g. 1-1000 kV, such as 12, 24 or 36 kV, of prior art normally comprise one to five modules housed in a casing, or encapsulation, and each module comprises at least three electrical bushings (one for each phase of a three phase AC power distribution system), conductors leading from each electrical bushing to a respective breaker, e.g. a vacuum interrupter, selector switches (one for each breaker), and busbars (one for each phase). The selector switches are used for connecting the breaker to the busbars or disconnecting them from the latter. Each selector switch normally comprises a switch knife movable between positions in which it is connected to or disconnected from the busbar.
The breaker is often a vacuum interrupter, which may be spring loaded, and is provided to interrupt the electric circuit upon occurrence of specific operational conditions. After such breaking, the selector switches may be manually or automatically disconnected from the respective busbar, either to a position in which the selector switch is connected to ground or an open position in which, for example, electric measurements on the components on the breaker side of the switch may be performed.
Examples of switchgears are disclosed in each of US2008/0217153 A1, US2004/0104201 A1 and DE 3528770 A1, in which a switchgear is disclosed, which for each phase has a breaker, a busbar and a movable switching element which is pivotable between a first position, in which the switching element electrically connects the breaker to the busbar, a second position, in which the switching element is connected to ground/earth, and a third position in which the switching element is disconnected from both the busbar and ground, the third position corresponding to a switched-off position.
US 2005/0241928 A1 discloses an electric power interrupter with an internal contactor for use as a line or load switch constructed from light weight materials.
U.S. Pat. No. 3,919,511 discloses a circuit breaker equipped with a mechanism housing which is partly covered by half-shells consisting of electrically conductive material in order to not impair the electric field in the interior of the breaker housing.
U.S. Pat. No. 5,057,654 discloses an interrupter switch assembly provided with an interrupter unit having a moulded housing and a cover portion with which a conductive portion of a conductive shunt current path is integrally moulded, the conductive portion being generally a thin member or strip.
US 2002/0179571 A1 discloses an electrical circuit interrupter device for a power distribution system, comprising a housing made of a conductive material, e.g. aluminium, forming part of the electrical connection between a first terminal and a second terminal. The housing is connected to a circuit interrupter, e.g. a vacuum interrupter, situated between the first terminal and the housing, and the housing houses a manual handle and lever mechanism assembly for operating the circuit interrupter. Alternatively, the housing is made of a non-conductive material with a conductive shunt forming part of the electric connection between the first and second terminals.
WO 2004/032298-A1 discloses a gas-insulated switch of a compact structure including a vacuum interrupter, where components are fixed to and electrically connected to conductive cases for mitigating the electric field of a movable contact unit of each component.
U.S. Pat. No. 5,003,427 discloses a metal enclosed multi-phase high voltage switching arrangement, including a busbar, a power switch and a three-way switch.
U.S. Pat. No. 5,276,286 discloses an exposed outdoor disconnector for operating under icing conditions, including a vacuum switch mounted to a protective metal cover, the metal cover housing members for operating the vacuum switch. JP2001 143582-A discloses a vacuum breaker connected to a housing. WO 01/78100-A1 discloses an isolating circuit breaker for pole mounting including a vacuum interrupter mounted to a housing made of a metallic material, and the housing houses a guiding member for operating the vacuum interrupter.
EP2 180 490-A1, US 2008/0217153-A1, US 2004/0104201-A1 and DE 35 28 770-A1 disclose a switching device comprising a breaker and a switch element pivotable about a pivot axis between three positions. In a first position the switch element is electrically connected to the breaker and a bus bar. In a second position the switch element is electrically connected to the breaker and a grounded element. In a third position the switch element is disconnected from both the busbar and the grounded element.